Electric furnace



F. W. SPERR, 1a., AND H. J. ROSE. ELECTRIC FURNACE. APPLlCATlON FILED MAR 14'. 192].

Ptented June 6, 1922.

2 SHEETSSHEET 1.

gn'uemtoza wm x @51 M -F. W. SPERR, 112., AND H. J. ROSE.

ELECTRIC FURNACE. APPUCATION FILED MAR 14, I921- Patented June 6, 1922.

2 SHEETSSHEET 2.

UNITED STATES PATENT OFFICE.

FREDERICK W. SPERR, JR, AND HAROLD J. ROSE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS TO THE K OPPERS COMPANY, OF PITTSBURGH, PENNSYLVANIA, A COR- PORATION OF PENNSYLVANIA.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented June 6,1922.

To all whom it may concern:

Be it known that we, FREDERICK \V. SPERR, J r., and HAROLD J. Ross, both citizens of the United States, and residing at Pittsburgh, Allegheny County, Pennsylvania, have invented a new and useful Improvement in Electric Furnaces, of which the following is a full, clear, and exact description.

The present invention relates to furnaces, and more particularly to electric furnaces for testing materials. The present invention is illustrated as embodied in an electric furnace for heating coal samples.

The object of the invention is to produce a furnace of this character in which the heating can be accurately and readily controlled. The furnace is so constructed that when used for heating a tube containing a coal sample, the sample may be heated progressively in such a way as to closely simulate the coking conditions of a byproduct coke oven.

Tn the drawings in which is illustrated the preferred embodiment of the invention,

Figure 1 is a central longitudinalvertical section of the furnace;

Figure 2 is a plan view;

Figure 3 is a transverse vertical section;

Figure 4 is an end view partially in .Section of one of the heating units;

Figure 5 is a side view of one of the units;

Figure 6 is a detail view showing one of the electrical connectors; I

Figure 7 is a sectional view through the coal testing tube, and

Figure 8 is a. diagram of the switchboard connections.

Referring to the illustrated embodiment "of the invention, the furnace indicated generally by reference numeral 2 has a long open top heating chamber 3. This heating cham her is formed by a plurality of U-shaped heating units 4:, one of which is shown in detail in Figures Land 5. In the illustrated embodiment of the invention eighteen of 45 such heating units are shown, although the number may be varied to suit conditions.

The heating units 4 are made up of U-shaped pieces of refractory material. For this purose we have found alundum to be a suitable 50 material. The alundum core or block 5 has formed in it a spiral groove in which is wound the resistance wire 6. After the unit is wound the wire is coated with a layer of cement 7 preferably alundum cement. This serves to protect the resistance wire. The heating units are placed end to end, as shown in Figures 1 and 2. The resistance units are enclosed in a suitable refractory heat insulating material. Suitable materials for this purpose are the heat-insulating refractory brick sold under the trade names of Sil-ocel or Nonpareil brick. As shown in the drawings a brick 8 forms the base of the furnace and two bricks 9 and 10 are placed "on each side of the row of heating units.

The whole furnace is enclosed in a box or outside covering 11 of asbestos board. One end of the furnace is closed by a solid brick 12 of heat-insulating material. The other end of the furnace is closed by another brick 13 of heat-insulating material. This brick has a hole 14 through which is passed the coal testing tube 15. The brick 13 has a sliding joint 16 with the body of the furnace so that it may be raised and lowered to raise and lower the coal testing tube in the furnace.

In Figure 7 is illustrated more in detail the coal testing tube, which is an old and well known piece of apparatus for testing the coking and byproduct qualities of the coal. As the coal testing tube is used, the end of the tube for about twelve inches is filled with a sample of powdered coal 17. Then two asbestos plugs 18 about an inch each in length are inserted. Through these plugs is a small opening 19 for the escape of the gases. Beyond the plugs 18 the tube is filled with fragments of sillca brick held in place by a small plug 'or partition 21. In testing the coal the portion of the tube containing the silica brick 20 is first heated to the desired temperature which may be from 800 to 850 degrees centigrade. Then the coal in the tube is heated progressively beginning at brick. In this way the coking conditions of the by-product oven are simulated and the coal may be tested for its byproduct yields.

The resistance units are so connected as to get the proper and progressing heating of the testing tube. The various heatin units are connected to switches S carrie on a switchboard 22 which is supported by the brackets 23 from the furnace. The units of the furnace which enclose the silica brick the end of the coal next the silica of electric energy,

portion of the tube are connected in parallel and to a single switch S, as shown in F igure 2. An'adjustable rheostat R is inserted in the circuit whereby the heatin of these units is independently regulable. Tf desired, a separate source of current ma be employed for heating these units. 11 of the other heating units are individually connected to similar switches. The leads 30 and 31 of a heating unit are connected to the blades of a double-pole double-throw switch S. The stationary contacts of the switches S are connected to two sets of bus-bars or feeders 32 and 33, and 34 and 35, respectively, as shown in Figure 8. The bus-bars 32 and 33 are connected to some suit-able regulable source of electric current. For this purpose we have used the ordinary 110-volt building lighting circuits controlled with a voltage regulator, giving a voltage range of from 10 to 110 volts: The busbars 34 and 35 are connected to a separately controlled source for example,.a second voltage regulator, so that the voltage of the bus-bars 34 and 35 may be regulated independently of the voltage of the bus-bars 32 and 33.

In operating the furnace, the coal testing tube is filled with a coal sample as above described and then pushed through the hole 14 into the furnace. The switch'controlling the three resistance units surrounding the silica brick section of the tube is then closed and the silica brick brought to the proper temperature. After this the other heatlng units are thrown in progressively to heat the sample of coal 17. The heat of any of the units may be varied relative to the other units by throwing the switch controllin unit in question from one set of bus-bars to the other set of bus-bars. The heating .of the furnace as a whole may be varie by changing the voltage-'regulator or regulators.

A typical example of regulation for. testing the coal samples is as follows :-After the tube containing the coal sample is put into the furnace, the switch S is closed and the silica-containing portion of the tube is heated to a temperature of from 800 to 850 degrees centigrade. The current through the units controlled by the switch S is thereafter maintained so as to keep the silica brick portion at this temperature throughout the test. After the silica brick portion has been thus heated, the remaining heating units are thrown in progressively. The voltage on one of the sets of bus-bars is adjusted higher than that on the other set of bus-bars.

higher voltage set of bus-bars to become more quickly heated, and after it'is sufficiently heated, it is thrown on the other or lower voltage set of bus bars. The voltage of this second set of bus-bars is Each unit is first thrown on the lowered from time to time, as less voltage is required to maintain the furnace temperature as more units are thrown into circuit. The voltage is regulated So that substantially the same temperature is maintained at eac unit throughout the run. I Thermocouples may be inserted in the furnace to check up the temperature.

After the three or four units of the tube to the right of the asbestos plugs 18, as shown in igure 7, are heated, the resistant unit or units opposite the asbestos plugs 18 may be cut out of circuit, if desired. This prevents undesirable cracking of the gas passing through too highly heated asbestos plugs.

The heating of the tube may also be Varied by varying the vertical position of'the tube in the furnace chamber. By raising the tube nearer to the top of the furnace chamber, the heating may be lessened and particularly the heating of the upper part of the tube. Thus by raising the tube, the top of the tube above the coal sample along which pass the gases may be maintained at a somewhat lower temperature than the bottom of the tube where the coal is, and in this way the effect of a byproduct oven having a comparatively cool top may be simulated.

The heatingof the tube may also be varied if desired 'by board on top of the furnace to,m0re or less cover the open top of the furnace chamber.

.The heating units can be readily taken out of the furnace and replaced by other units in case they burn out or are damaged. For this purpose the ends of the resistance wire are connected with the copper leads to the switches by means of the screw connectors 40, one of which is shown in Figure 6.

The legs of the U-shaped cores 5 have holes 41 through which are passed the free ends of the resistance wires. This is a convenient way for holding the ends of the wires and forkeeping the wire from unwinding on the units.

While we have specifically illustrated and 'described the preferred embodiment of our 1nvention, it is to be understood that the invention is not'limited to its illustrated embodiment, but may be otherwise embodied within the scopeof the following claims:

We claim? 1.- An electric furnace, of heating units forming narrow heating chamber to receive a testing tube, and means for connecting in circuit the units progressively from one end of the row to the other so as to progressively heat the sample of material being tested, substantially as described.

2. An electric furnace, comprising a furnace chamber formed by a row ed heating units, substantially as described.

3.'A1 1 electric furnace, having an open comprising a row plac1ng piecesof asbestos a relatively long of open end-.

describdd.

4. An electric furnace, comprising a heating chamber formed of a plurality of U shaped heating units of refractory material wound with resistance wire, substantially as described.

5. An electric furnace having a long open sided heating chamber adapted to receive a testing tube and having provision of varying the position of the tube in the chamber, su stantlally as described.

6. An electric furnace, comprising a long heating chamber open atthe top side and adapted to receive a testing tube, and having provision for the vertical adjustment of the'testing tube in the furnace chamber, substantially as described.

7 An electric furnace, comprising a plurality of heating units and a plurality of separately regulated feed lines, and switches for connecting different units to different lines, substantially as described.

8. An electric furnace, having a relatively long heating chamber adapted to receive a testing tube and having a relatively I longlongitudinally extending opening in its side, substantially as described.

9. An electric. furnace, having an open sided heating chamber, a front closure for the chamber throu h which may be inserted a testing tube, sai frontclosure being arranged to slide relatively to the body of the furnace so as to vary laterally the position of the testing tube in the furnace chamber, substantially as described. I

10. A heating unit for an electric furnace, comprising a 'U-shaped core of refractory material, and a winding of resistance wire on the core, substantially as described.

11. A heating unit for an electric furnace, comprising a U-shaped core of refractory material, a winding of resistance wire on the core, said core having holes through its legs to hold the free ends of the wire, substantially as described. e 12. An electric furnace, comprising a plurality. of independent heating units, means for temporarily applying a higher voltage to each unit to raise it rapidly to the desired temperature'and. for thereafter applying a lower voltage to maintain it at this temperature, substantially as described. v 13. Anelectric furnace, comprising a plurality of independent heating units, means for throwing the heating units progressively into circuit comprising means for first applying a higher voltage to a unit when first thrown into circuit to raise it quickly to the desired temperature and for thereafter applying a lower voltage, substantially as described.

14. An electric furnace, comprising a furnace'chamber formed of a row of openended heating units, means for progressively applying current to the units, comprising means for firstapplying the current at a higher voltage to each unit to raise it rapidly to the desired temperature and for thereafter applying the current at a lower voltage to maintain this temperature, substantially as described.

15. An electric furnace for testing coal samples,

comprising a relatively long horizontal furnace chamber for the reception ofa coal testing tube, and electric means for progressively heating the sample from end to end so as to simulate the coking conditions of a by-product coke oven, substantially as described.

16. An electric furnace for testing coal samples, comprising a relatively long furnace chamber for the reception 0 a coal testing tube, and electric means for progressively heating the sample from end to end and maintaining the increments of said sample in a heated condition until the sample is heated to a substantially uniform temperature, substantially as described.

17. An electric furnace for testing coal samples, comprising a relatively long fur nace chamber for the reception of a coal testing tube and having a longitudinally disposed row of heating units, and means'for regulating the heating units adjacent to the cracking zone of the tube independently of the units adjacent to the coal-containing ortion of the tube, substantially as descri ed.

18.. An electric furnace for testing coal samples, comprising a relatively long furnace chamber for the reception of a coal testing tubeand having a longitudinally disposed row of heating units, and means for first switching current to heat the units adjacent to the crackin zone of the tube and thereafter for switc ing in one by one the heating units adjacent to the coal-containing portion of the tube to heat the sample progressively from end to end while maintaining the cracking zone heated, substantially as described.

,In testimony whereof, we have hereunto set our hands.

FREDERICK W. SPERR,

JR. HAROLD J. ROSE. v

progressively heated 

